The present invention relates to fluorescent picture element tubes with high luminance, more particularly to high luminance color picture element tubes and display units constituted by the same for large area or giant area display panels.
In conventional case, especially in outdoor case, of employing large area or giant area displays, it is usually required that a display device have a luminance of several thousand candelas per square meter because of rather intensive ambient illumination, and it is impossible to offer a sufficiently large display area and high luminance by using a single display device because the display area is often several square meters or more. Therefore, a plurality of luminous picture element components have been used to constitute a display panel, and each of them represents a pixel in the picture displayed on the panel. By means of the circuits electrically connected with each of the picture element components, the instantaneous luminance given by each picture element component corresponds to that of the corresponding picture pixel, so that the picture is contituted on the display panel. Since the luminance and the total light output all over the panel surface are directly determined by the luminance of picture element components, the primary problem to be solved. is to increase the luminance of each picture element component for the purpose of applying the display panel in outdoor case.
In the prior art, incandescent lamps have been used as the picture element components. Since the maximum luminance of the incandescent lamp can be effected by selecting the maximum rated electrical power thereof, the luminance problem of the picture element components is able to be solved. Now this mode is still frequently used for high luminance character displays outdoors. However, the incadescent lamp has the disadvantages of high power consumption, low efficiency, slow response, and low reliability; also the fact that all of the power passes through the control circuit makes it expensive to construct the circuit. Therefore, the Flood Beam CRT (FBT) was invented in Japan a few years ago (disclosed in "Displays" a October, 1983, pp 207-211).
The FBT is an approximate 1-inch diameter CRT without any deflection system, including an electron gun and a phosphor screen emitting light at its one end. One FBT represents one pixel, and tens or even hundreds of thousands such FBTs, whose quantity used depends on the requirements of panel size and resolution and other factors, are arrayed in accordance with a certain mode to construct the large or giant picture or character display panel. The application of the FBT overcomes the defect of the dot-point matrix display panel constituted by incandescent lamps to a certain degree. Furthermore, since each pixel may comprise three monocolor FBTs, according to the instantaneous color and luminance of the pixel, the corresponding monocolor FBT instantaneously illuminates to well effect the color reproduction and to make the color display all over the panel possible. The quality and luminance of the picture can also meet the requirements of application.
However, because each FBT is a small picture tube in itself, the cost may be too high for the giant display system which requires tens or even hundreds of thousands FBTs. Moreover, in order to obtain the required luminance, the high voltage applied to the FBT is as high as 8 to 10kV, this gives rise to a series of problems, such as unreasonably high technical specifications, difficulty of delivering high voltage, and high cost caused by the high voltage circuit. In particular, in the case of outdoor operation, during rainy days or wet season, the humid atmosphere causes difficulty for high voltage isolation and even high voltage accidents. The application of high voltage also makes trouble in maintenance.
It is an object of the present invention to provide a fluorescent picture element tube with high luminance, which is used for large area or gaint area display and capable of operating at low voltage and offering sufficiently high luminance.
It is another object of the present invention to provide a fluorescent color picture element tube with high luminance, which is capable of operating at low voltage and emitting light including three primary-colors of red, green and blue. Each picture element tube becomes a color pixel.
It is a further object of the present invention to provide a fluorescent color picture element display unit which is constituted by a plurality of picture element tubes or tubes arrayed in line or in an mxn (m n are positive integers, and mxn.gtoreq.2) matrix, and represents one or more color pixels.